How do you remove the object line between two objects when joined?
You can't sculpt 2 objects at the same time, and even joining the 2 objects won't be enough to create a weld between the 2 as they will still be 2 separate meshes. What you need to do is either keep them 2 separate objects and use the Boolean modifier, or join them and use the Boolean tool (the one I explain below). In both case make sure that the mode is Union
Boolean tool: Join the 2 objects (ctrlJ), go in Edit mode, select one of the 2 meshes, go in the header menu (or press ctrlF) &gt; Face &gt; Intersect (Boolean), then in the Operator box choose Union.
Now you can sculpt the way you want.